This application is submitted for a video-rate confocal microscopy facility for intravital microscopy in living small. animals, such as genetically altered mice, in living cells rolling in a flow chamber and viable tissue maintained in tissue culture. We wish to merge three advanced technologies to develop our understanding of vascular disease, skin disease, thrombosi, cell signalling and cell: (1) intravital microscopy of blood vessels in living mice to study the impact of various perturbations of the vascular system on endothelium, leukocytes, platelets and plasma proteins including the blood clotting proteins; (2) the generation of mice altered by the knockout strategy or rendered transgenic, with the net effect of creating a protein deficiency or introducing a fluorophore into a protein of interest; (3) the development of video speed confocal microscopes, such as the BioRad RTS2000 and Noran OZ confocal scanning laser microscopes, that permit rapid, video rate, real-time data acquisition at high resolution. A consortium of investigators at Harvard Medical School has been established that have a special need for a video rate confocal microscope facility. This group is composed of a group of junior and established investigators who have a special need for video-rate confocal microscopy as it can be applied to their NIH-funded research programs. No such instrumentation is currently available at Harvard Medical School or its affiliated hospitals. The video-rate confocal microscopy system must include the following critical features: (1) An intravital microscopy facility for the use of live animals; (2) A laser confocal microscope system capable of rapid scanning and suitable for DIC and fluorescence microscopy under flow conditions; (3) A computer workstation with imaging software for image acquisition and reconstruction; (4) Multiple fluorescent channels for co- localization experiments. The BioRad RTS2000 real-time laser confocal system, fitted to a Nikon E600FN microscope, will provide a group of investigators with instrumentation to significantly advance their fields.